Browsing by Author "Notman, Hugh"
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- ItemOpen AccessThe Acoustic Structure and Ontogeny of Vervet Monkey Vocalizations(2019-11) Dubreuil, Colin; Notman, Hugh; Pavelka, Mary McDonald; Henzi, Peter; Hare, James; Fedigan, Linda Marie; Barclay, Robert Malcolm RuthvenVervet monkey (Chlorocebus pygerythrus) vocalizations have been the subject of considerable research, most notably for their putative language-like qualities. While this focus has inspired a productive research effort investigating vocal communication in non-human primates, it has diverted attention away from other, non-linguistically inspired mechanisms by which vocal signals exert their effects on receivers. My research focuses on two vocal classes, grunts and alarm calls, and how their acoustic structures vary according to sender-specific attributes, including age, sex, body size, and identity - all of which have the potential to influence receiver response. I recorded calls from three wild groups of vervet monkeys over a 7-month period on the Samara Game Reserve, South Africa. I used random forest models to determine whether grunts varied in structure in relation to caller age, sex, identity and context, and whether alarms varied with sex and caller identity. I performed a cluster analysis to determine whether alarms segregated into different call types based on variation in acoustic structure. Finally, I used a series of mixed effects models to determine whether call structure in males and females correlated with overall body size (using body weight as a proxy). I found grunts varied in structure with age and sex, but not among individuals or contexts. Alarm calls varied with both sex and identity. My cluster analysis identified two qualitatively distinct alarm call types corresponding to the calls of males and females respectively. My analysis demonstrated that the relationship between body weight and the distribution of acoustic energy throughout alarm calls differed between the sexes. Relative to females, acoustic energy in the calls of males was concentrated at disproportionately lower frequencies. These results suggest that alarm calls may be under selection to exaggerate caller body size and/or extend the effective range of these signals in males. My results highlight that vocalizations can vary in structure along a number of dimensions simultaneously. While it is possible that in some instances, vocalizations convey specific information surrounding their context of production, it is likely that the mechanisms by which vocal signals exert their effects on receivers are more numerous and diverse.
- ItemOpen AccessThe Colourful World of Platyrrhine Monkeys: Skin Colour Variation and Its Potential Role in Communication(2022-09) Alves Antonio Moreira Pacheco, Lais; Melin, Amanda; Higham, James; Pavelka, Mary; Notman, Hugh; Smith, Andrew; Vamosi, JanaUnderstanding the evolution of human communication has been a longstanding goal of anthropologists and has spurred many lines of research. Studying our closest living relatives, the non-human primates (NHPs), provides an opportunity to better understand human communication, by placing it in a comparative context. Among NHPs, use of colour signals is common and widely distributed across the Order. Catarrhines have trichromatic colour vision and exposed skin colouration plays an important role in their interactions. In platyrrhines, exposed skin is less common, but some genera have widely exposed body regions, suggesting that skin colouration might also be used for communication. Intriguingly, platyrrhines have polymorphic colour vision, in which some individuals are dichromats while others are trichromats. This polymorphism may affect signal perception by conspecifics and shape some aspects of communication. However, we currently lack studies measuring colour (hue, saturation, chroma) variation in their skin. In this thesis, I provide several studies that seek to explore the potential for colour signals in platyrrhines. I provide the first analysis of the distribution and evolution of facial skin exposure and colour in platyrrhines in Chapter 2. I then report in Chapter 3 variation in facial skin colour of golden lion tamarins (Leontopithecus rosalia) in the context of breeding status, reproductive condition, and age. In Chapter 4, I investigate if female genital skin colour of two species of wild tamarins [saddleback (Leontocebus weddelli) and emperor tamarins (Saguinus imperator)] vary between developmental classes. Finally, I study the hypertrophied and pendulous clitoris of female black-handed spider monkeys (Ateles geoffroyi) and investigate if its colour and shape varies within and between individuals. My results suggest that among platyrrhines there is extensive variation in skin exposure and colouration and that colour seems to be linked to breeding status, reproductive condition and age in some species, and colour variation occurs within and between individuals. These results show potential for convergence in some functions of bare-skin signaling in catarrhine primates. My Doctoral Thesis makes contributions to the understanding of primate communication by adding new comparative data to illuminate the selective pressures shaping the sensory and communication systems across our order.
- ItemOpen AccessFission-Fusion Dynamics in Spider Monkeys in Belize(2016) Hartwell, Kayla Song; Pavelka, Mary; Notman, Hugh; Fedigan, Linda; Sicotte, Pascale; Ruckstuhl, Kathreen; Chapman, Colin; Dawson, PeterMost diurnal primates live in cohesive social groups in which all or most members range in close proximity, but spider monkeys (Ateles) and chimpanzees (Pan) are known for their more fluid association patterns. These species have been traditionally described as living in fission-fusion societies, because they range in subgroups of frequently changing size and composition, in contrast with the more typical cohesive societies. In recent years the concept of fission-fusion dynamics has replaced the dichotomous fluid versus cohesive categorization, as it is now recognized that there is considerable variation in cohesiveness both within and between species. This thesis is a study of the fission-fusion dynamics in spider monkeys to quantify and explain temporal variation in subgroup size, spatial cohesion, and stability. I collected behavioural, ecological, and genetic data from a group of spider monkeys at Runaway Creek Nature Reserve in Belize from January 2008 until September 2013. I found that most subgroups were small (1-3 individuals), contained only adult females, and changed membership every 30-40 minutes. Habitat-wide fruit availability showed a weak relationship with subgroup size, contrary to what I expected, but it did explain some of the variation in subgroup stability. Likewise, degree of relatedness between individuals was not correlated with an association index that measured the likelihood that any two individuals would be in the same subgroup together. This thesis also describes the feeding ecology of the study group, and explores their genetic structure. The latter revealed some unexpected patterns: although traditionally believed to be a male philopatric, female dispersal species, male spider monkeys at Runaway Creek were no more closely related to one another than were females, and both males and females were residents and immigrants. As expected, given the common characterization of spider monkey males as experiencing low levels of within-group competition for females, paternity analysis revealed no reproductive skew, with all males siring offspring. Further analysis is needed to identify and understand the variables that are affecting the temporal changes in subgroup size, spatial cohesion, and stability of this group. However, this study makes an important contribution to this much larger question.
- ItemOpen AccessMaternal and Nonmaternal Infant Handling in Colobus vellerosus(2018-05-09) Gibson, Allyson; Sicotte, Pascale; Notman, Hugh; Fedigan, Linda MarieThis project investigated whether variation existed in durations of maternal and nonmaternal received by infants (when controlling for infant age) in wild Colobus vellerosus monkeys. I examined whether variation in handling durations was associated with infanticide risk using behavioral data collected from 16 infants ranging in age from newborn to 78 weeks. Maternal handling constituted the bulk of ‘total’ handling received by infants. Individuals varied in the duration of handling they received. Less maternal handling occurred in unstable groups, and male infants receiving more handling. Neither maternal nor nonmaternal handling responded to all infanticide risk factors. These results suggest that handling is a flexible behavior, but it is not yet entirely clear what factors handlers respond to, and why. One potential explanation is that, when infanticide poses a higher threat, mothers decrease infant-contact time to facilitate faster infant development while nonmothers increase handling as a form of protection.
- ItemOpen AccessSex Differences in the Use of Whinny Vocalizations in Spider Monkeys (Ateles geoffroyi).(2014-01-20) Dubreuil, Colin James; Pavelka, Mary; Notman, HughSpider monkey social groups are characterized by male philopatry and high fission-fusion dynamics. Individuals form subgroups that temporally vary in size, composition, and spatial cohesion. Both sexes produce whinny vocalizations, which may allow close associates to maintain contact in dispersed subgroups. Females however do not form close bonds, therefore the use of their call remains unresolved. We investigate sex differences in the use of whinny vocalizations by the Yucatan spider monkey (Ateles geoffroyi yucatanensis) at Runaway Creek Nature Reserve, central Belize. Females called at higher rates than males in most behavioral contexts, particularly while foraging. The likelihood of female calling increased during subgroup fissions and fusions, and was positively correlated with the number of animals joining or leaving a subgroup. Neither behavioral context, nor changes in subgroup composition affected the likelihood of calling by males. These different patterns indicate that the call may function differently for each sex.
- ItemOpen AccessThe meaning, structure and function of chimpanzee pant hoots from the Budongo forest, Uganda(2002) Notman, Hugh; Pavelka, Mary S. McDonaldPant hoots are the species-typical loud calls produced by chimpanzees to communicate to conspecifics over long-distances. Previous studies have attempted to determine the degree to which pant hoots function as referential signals that communicate information specific to behavioural, social and ecological contexts but have produced mixed results. Uhlenbroek (1996, unpublished PhD thesis) identified three acoustically and functionally distinct sub-classes in pant hoots produced by chimpanzees from the Gombe Stream Reserve, Tanzania. Uhlenbroek labelled these variants "roar," "slow roar" and "wail" pant hoots and proposed they serve a referential function by being used in specific contexts. In this study, pant hoots were analyzed to determine whether similar functionally distinct vocal classes could be discerned in the Sonso chimpanzees of the Budongo Forest, Uganda. Using cluster and discriminant function analyses, three pant hoot types were identified quantitatively and a fourth type described qualitatively. Three of these pant hoot types exhibited varying degrees of production context specificity. However, contrary to Uhlenbroek, a strictly referential function for pant hoots is not proposed. Rather, I suggest that the structural characteristics of pant hoots are constrained by environmental, physiological and phylogenetic factors, and that the acoustic design of different pant hoot types conform to predictions concerning both motivational effect and propagation maximization in specific "layers" of the acoustic habitat. In addition, I propose the hypothesis that other acoustic cues, such as the presence of buttress drumming, the number of animals calling, the rate of calling per episode and the location of the caller relative to the ground, accompany many calls and are used by receivers to gauge the context and relevance of the call in determining a future course of action. In this manner, pant hoots might function referentially in a "weak" sense in that the interplay between the type of pant hoot produced and the suite of accompanying cues provide information concerning the context and "meaning" of the call.